This invention relates to chocolate refiner having universal operation characteristics.
As is known in the art, chocolate refiners functions to impart chocolate with a determined fineness or grain size, while making it as homogeneous as possible. The fineness degree aimed at is dictated by the subsequent utilization of the chocolate. For chocolate products of fine quality, degrees of fineness in the order of about 15-30 .mu.m are usual. That fineness is achieved by successively squeezing the chocolate through a plurality of refining roller pairs which are spring loaded in succession against each other, the inlet pair forming the feed-in roller pair and the last of the rollers forming the delivery roller.
With such prior machines, one can adjust the pressure on the individual rollers either separately or simultaneously on all rollers. The latter are set apart from each other to form a nip through which the material entrained therealong by adhesion is caused to pass. The speeds of the individual rollers increase from the inlet roller pair to the delivery roller. Conversely, the thickness or depth of the chocolate film will decrease from the inlet roller pair (e.g. at about 100-400 .mu.m) toward the delivery roller (e.g. to 15-30 .mu.m). The refining action results from a simultaneous compression or squeezing action, and a drawing or shearing action exerted on the chocolate film. The refining rollers are currently quite wide. e.g. up to about two meters wide. Accordingly, it is specially difficult to maintain such small thicknesses over such great widths with those rollers.
It is known to control the thickness of the chocolate film being delivered by varying the pressure of the refining rollers, in particular of the feed-in roller pair.
Owing to high pressure levels being used between the rollers during the refining process, the roller surfaces tend to flex inwardly, along the opposed generatrices thereof, resulting in the formation of an increased depth slit at the middle. This phenomenon is made quite appreciable by the refining rollers being of hollow construction, i.e. constructed to convey a cooling medium through their interiors, that is a medium effective to remove the heat generated during the refining process. To oppose that hogging tendency, it is known to construct the refining rollers with a degree of compensating counter-crown. The latter will, of course, be taken up in operation by a set working pressure in the presence of a product having a given viscosity. Refiners have, therefore, been constructed heretofore for given thicknesses of the chocolate films to be delivered. As the viscosity of the product to be processed varies, e.g. between batches, an attempt is made at maintaining the desired fineness by changing the roller pressure, the rollers being carried in slidable supports mounted in the machine frame.
In actual practice, it has been found that in spite of the control exerted on the refining roller support pressure, it is very difficult to achieve and maintain the desired degrees of fineness as the viscosity of the product to be processed changes, particularly where high production outputs are aimed at. Of course, for each individual refiner, the amount of crowning for each roller is determined in accordance with the experience gained by the manufacturer in relation to the characteristics of a product to be refined.
Thus, with one prior refiner, it is impossible to provide a product film having a fineness which deviate appreciably from the machine fineness rating. With products whose viscosities are markedly different, the user has been obliged heretofore to purchase a range of refiners. As an example, in the United States, highly liquid pastes are often used, whereas in Germany and Greece quite different pastes are often adopted. While this does not represent a major difficulty for large chocolate producers, the cited limitation to prior refiners may be economically unacceptable for small producers, who have been forced to modify the formulations and technological cycles of their products to meet the requirements of prior refiners and make the products processable on such machines. This reflects sometimes unfavorably on the characteristics of the finished product, because a change in the fat content of the chocolate paste, as made necessary in order to make it processable, would later affect the refining operation, which is known to impart the final product with its specific taste.
Alternatively, where the preset crowning fails to provide a product having a desired fineness, or where the product viscosity changes, it has been common practice heretofore to mechanically manipulate the machine itself. That manipulation may affect the amount of crown and roller speeds. In the former case, the rollers must be disassembled and returned to the machine manufacturer, thereafter they are delivered back to the user for reassembling, which operation usually takes some weeks. In the latter case, since speed changes would generally be small, the roller gears have to be altered or replaced. Both operations are of an empirical nature and carried out by trial and error, depending on one's experience, thereby they may be easily unsuccessful, and in all cases quite expensive, time-consuming, and the cause for considerable downtime.